1. Field of the Invention
The present invention relates to an electromagnetically actuated adjusting apparatus for lens, more particularly an adjusting apparatus that uses magnetic flux produced by coils to push the permanent magnet arranged on the body of lens for shifting the position of lens body.
2. Description of the Prior Art
Driven by technological advances and strong consumer demands, all kinds of information products and equipments are conceived and borne, in which camera is a significant invention. In the electronic age, portability is an essential requirement for camera. Thus the design and manufacture of camera are directed towards small size and lightweight.
Lens has always been one of the key components that influence the photographic quality of a camera. During photographing, lens position sometimes needs shifting or fine tuning to adjust its aperture or shutter speed in response to the intensity of light, or to change the image magnifying power or fine tune image clarity so the camera lens can zoom or focus.
Referring to FIG. 1 which is a schematic diagram showing the side view of a conventional mechanically-driven lens position shifting means, the lens position shifting apparatus comprises a lens 11, a first connecting member 12, a second connecting member 13, a threaded pole 14, a guide rod 15, and a motor 16. The first connecting member 12 and second connecting member 13 are respectively adjoined to the top and bottom of lens 11, and the first connecting member 12 is linked to threaded pole 14, while the second connecting member 12 is linked to guide rod 15. When the lens position needs to be shifted, the motor 16 drives the threaded pole 14 to rotate in forward or backward direction that sets lens 11 to undergo corresponding linear displacement 92 between threaded pole 14 and guide rod 15 to adjust the lens 11 position. But because mechanically-driven lens position shifting apparatus tends to be bulky, consumes more power, and costs more with its precision mechanical positioning, only few conventional cameras still use such means, while practically no digital camera nowadays employs such mechanically-driven lens position shifting apparatus.
Digital camera uses instead an electromagnetically actuated lens position shifting apparatus. FIG. 2A and FIG. 2B are respectively a perspective view and a side view of the conventional electromagnetically actuated lens position shifting apparatus 2. Such apparatus 2 consists of a lens 21, a permanent magnet ring 22, a first coil assembly 23 and a second coil assembly 24. The permanent magnet ring 22 is adjoined to lens 21 with a first polarity 25 and a second polarity 26 at each end respectively. The first coil assembly 23 and the second coil assembly 24 are respectively wound on each side around the periphery of lens body 21 and correspond to the first polarity 25 and second polarity 26.
When the lens position needs to be shifted, the first coil assembly 23 and the second assembly 24 are charged to generate magnetic flux lines in a specific direction (i.e. along the axial direction of lens 21), which could propel the permanent magnet ring 22 to the left or right along the axial direction of lens 21. As such, lens 21 moves towards a predefined direction to achieve the purpose of lens position shift.
However in the conventional electromagnetically actuated lens position shifting apparatus 2, coil assemblies 23 and 24 are wound around the periphery of lens 21 where magnetic flux lines converge at the center axis of lens 21, while magnetic flux lines at the position of permanent magnet ring 22 are not as concentrated in comparison. As such, the majority of magnetic flux lines emanated from coil assemblies 23 and 24 have no action, resulting in low efficiency and higher power consumption. In addition, the permanent magnet ring 22 has to be of comparable size in order to be propelled by the relatively weak magnetic flux. Consequently, the entire apparatus structure is bulky, and with winding around only two sides of the lens 21, the apparatus allows only two-position displacement of lens 21, which runs counter to the goal of small size and light weight. Thus improvement of the lens position shifting means has been an ongoing effort.